No description available.

L'objectif de cette thèse est de développer et d'évaluer des paramètres quantitatifs de l'IRM de la prostate en discriminant les cancers de score de Gleason (GS) ≥7. Nous supposons que les paramètres quantitatifs de l'IRM pourraient aider à standardiser le diagnostic, et à diminuer la variation inter-lecteur et/ou inter-institution du diagnostic du cancer de la prostate. Cette thèse est divisée en trois chapitres. Le premier chapitre, intitulé « IRM T2 quantitatif de la prostate », est une étude rétrospective sur une base de données des patients avant prostatectomie radicale. Le deuxième chapitre, intitulé « IRM multiparamétrique quantitative de la prostate », est aussi une étude rétrospective avant prostatectomie radicale. Le troisième chapitre, intitulé « Élastographie IRM de la prostate par voie trans-périnéale» est une étude expérimentale. Notre première étude montre que le T2 est robuste sur les machines de constructeurs différents. Le T2 est un prédicteur significatif, mais de faible performance, d'agressivité du cancer de la prostate à 3T. Notre deuxième étude montre que la combinaison du 10ème centile de l'ADC avec le Time-topeak (TTP) améliore la performance du diagnostic, et ce modèle est lui aussi robuste entre des machines de constructeurs différents. Notre troisième étude montre les résultats préliminaires sur l'élasticité de la prostate. Ces résultats montrent que l'élastographie IRM de la prostate en haute fréquence d'excitation (>100 Hz) par voie trans-périnéale est faisable. L'élastographie pourrait à l'avenir être intégrée à l'IRM multiparamétrique quantitative pour améliorer la performance de diagnostic / The purpose of this thesis is to develop and evaluate the quantitative methods of multiparametric MRI of prostate in discriminating Gleason score (GS) ≥7 cancers. We suppose that the quantitative parameter of MRI could help standardizer the diagnostic, reduce the inter-lecture and/ or inter-institution variation in diagnostic of prostate cancer. This thesis is divided into three chapters. The firs chapter, entilted « Quantitative T2 MRI of prostate » is a retrospective study on a database of prostate cancer patients before radical prostatectomy. The second chapter, entilted « Multi-parametric Quantitative MRI of prostate » is also a retrospective study before radical prostatectomy. The third chapter, entitled « MR elastography of prostate by transperineal approach », is an experimental study. Our first study shows that T2 value is robust between machines of different constructors. T2 value is significant predictor, but of weak performance, of aggressively cancer of prostate at 3T. Our second study shows that the combination of ADC_10th percentile with Time-to-peak (TTP) improved the diagnosis performance, and this model is also robust between two machines of different constructors. Our third study shows the initial results on elasticity of the prostate. These results show that MRI elastography of prostate at high excitation frequency (>100 Hz) by trans-perineale approach was feasible. The elastography may, in the future, be integrated in quantitative multi-parametric MRI to improve the diagnosis performance

No description available.

The hydrograph at the watershed outlet was simulated using the time-area curve concept implemented in a geographic information system (GIS). The goal of this study was to determine if hydrograph prediction accuracy would be improved by accounting for spatial and temporal variation of excess rainfall. Three models with different methods of estimating excess rainfall were developed: the Distributed Curve Number (DCN) model uses a CN for each cell, generating spatially distributed excess rainfall using the Soil Conservation Services curve number method (SCS, 1972); the Uniform Curve Number (UCN) model uses a single "average" CN for the whole watershed, thus generating a uniform excess rainfall; the Phi index model which uses the Phi-index method to generate uniform excess rainfall. With the aid of a GIS, the cumulative flow time to the watershed outlet is estimated for each cell in the watershed and the isochrones of equal travel time are developed. The time-area curve is developed in the form of an S curve. The spatially distributed 1-hr unit hydrograph is derived from the S curve as the difference between the S curve and its value lagged by 1-hr. The models used in this study describe the physical processes and flow mechanisms. They also reflect effects of watershed characteristics (slope, landuse, soil drainage potential) and excess rainfall intensity on the resulting hydrograph at the watershed outlet. Surface flow is divided into channel flow and overland flow based on the upstream drainage area. Flow is routed to the watershed outlet through a channel network derived from the watershed Digital Elevation Model (DEM). The models developed were tested against observed rainfall-runoff data from the 1153-ha Virginia Piedmont watershed (Owl Run). A total of 30 storms were simulated, with statistical comparison of peak flow rate, time to peak flow rate, and the hydrograph shape. The hydrograph shape was compared both visually and statistically. Results indicated that the two models which account for temporal variation in excess rainfall (DCN and UCN) predicted the output hydrograph much more accurately than the Phi model which lacks the ability to capture the temporal variation of excess rainfall. For this watershed, results showed that the spatial variability in excess rainfall which was accounted for by the DCN model did not improve the prediction accuracy over the UCN model which lacks that ability. However, a sensitivity analysis for the effect of the spatial distribution of the excess rainfall indicated that can be a significant effect of spatial distribution on the predicted hydrograph. / Master of Science